The present invention relates to a plastic film which has an enhanced anti-static property, and, therefore, which may advantageously be applied to magnetic tapes, floppy disks, flexible substrata, materials for membrane switches, recording sheet for printers, etc. Particularly since this is used for films which do not lose transparency, the film may also be utilized for films for OHP., liquid crystal display devices, touch panels, stained glasses, etc. Further, because its transparency is such excellent that does not have adverse influences on the photographic properties, the plastic film can also be applied to light-sensitive photographic materials. Particularly in the case of light-sensitive photographic materials, owing to its excellent properties, the plastic film can be applied not only to silver halide light-sensitive materials, but also to light-sensitive materials in which light-sensitive materials other than silver halide is used.
Generally, plastic films (hereinafter, they may also be simply referred to as "films") have a strong electrification property. Therefore, they are often restricted for their use except when they are utilized using this property per se. For example, In the field of silver halide light-sensitive photographic material (it may also be hereinafter simply referred to as "light-sensitive photographic material"), plastic films are commonly used as supports for their electrically insulating property. Since the light-sensitive photographic material is a compound material consisting of a support and light-sensitive photographic layers, it tends to be electrified easily due to contact friction or peeling between two surfaces of similar or different materials. Electrostatic potential accumulated by electrification causes a variety of hindrances. The most serious hindrance is that light-sensitive emulsion layers are subjected to light exposure upon discharge of the electrostatic potential electrified before development, causing spotty, or branch- or plumage-shaped marks, which are so-called "static marks". For example, when this phenomenon turns out in medical or industrial x-ray images, it can lead to very dangerous diagnoses or judgments. This phenomenon is one of the most difficult problems because this phenomenon becomes clear after development. Further the accumulated electrostatic potential can be a cause of other troubles of adhesion of dust onto the surface of films, or that even coating on the surface of films cannot be performed.
Such hindrances other than those mentioned above due to electrification, a lot more cases take place. For example, they may take place during manufacturing process due to contact friction of photographic film and rollers during winding of photographic films or upon separation of the surface of the rewinding of the surface of the emulsion from the surface of the support; and, moreover, due to mechanical contact with or separation of x-ray films from automatic x-ray photographing machines, fluorescent sensitizing screens or other packaging materials. Occurrence of such static marks becomes remarkable, with enhancement of sensitivity of light-sensitive photographic films or processing speeds of the same. Particularly, in recent years, due to enhancement of sensitivity, and coating and processing speeds, occurrence of static marks becomes more likely to take place.
Further, recently adhesion of dust after development has turned out to be a big problem and improvement in sustaining of anti-static property even until after development process has become requested.
The best way to eliminate these hindrances due to electrostatic charge, is to confer electroconductivity on the material and thus to get the accumulated electrostatic potential to be leaked and lost during a short period of time before discharge.
Accordingly, lots of attempts and proposals for improving electroconductivity of photographic supports or the surfaces of various coating layers have so far been proposed and application of various kinds of surface active agents, polymers, etc. have been attempted. For example, Japanese Patent O.P.I. Publications No. 49-91165(1074) and No. 49-121523(1974) disclose a technology of applying ionic polymers having a dissociative group in the main chain thereof. Beside the above, inventions concerning electroconductive polymers disclosed in Japanese Patent O.P.I. Publication No.2-9689(1990), No.2-182491(1990) and inventions concerning surface active agents disclosed in Japanese Patent O.P.I. Publications No. 63-55541(1988), No. 63-148254(1099), No. 63-148256(1988), No. 1-314191(1989),etc. are known.
However, many of these substances often show peculiarity depending on kinds or nature of film supports or photographic compositions. That is to say, although they can give favorable results to a certain kinds of film supports, photographic emulsions and photographic constituting elements, however, they cannot only give such helpful results at all as anti-static agents, purpose, but also do they often show adverse influences on the photographic properties. As further important disadvantage, most of these substances lose electroconductive function under low humidity conditions.
For the purpose of reducing degradation of the photographic properties under low humidity condition, Japanese Patent Publication Nos. 35-6616(1960) and No. 1-20735(1989) disclose a technology of using metal oxide as an anti-static agent. The technology disclosed in the former reference relates to a method of using colloidal dispersion, the latter disclosing a method of using powder of metal oxides having high crystallinity by treatment at high temperature. However in the latter reference, it is described that since powder having high crystallinity is employed, it is necessary for particle size and particle/binder ratio, etc. with respect to light scattering to be taken into account. Further in the technology disclosed in Japanese Patent O.P.I. Publication No. 4-29134(1992), for the purpose of improving not only properties under low humidity condition but also other defects, application of particulate and fibrous metal oxides is disclosed as electro-conductive elements has been disclosed, however, a problem on the amount of addition has still remained.
Recently, consumption of silver halide light-sensitive photographic material has continuously been increasing. Accordingly, amount of photographic materials to be processed has also been increased and, thus, still further demand for rapid processing, or increasing amount of processing speed in a predetermined period of time has been made. Therefore, it has been demanded that silver halide light-sensitive materials have stronger resistance against rough handling during processing operation. Still more, as environmental regulation has become stricter, processing with lower replenishment, decreasing amount of waste processing solution has also been necessary.
Among various photographic properties, anti-static property is one upon which tougher demand has been made. Heretofore, as anti-static agents used for the light-sensitive materials, high molecular weight electrolytes or surface active agents have been used. As these high molecular weight electrolytes and surface active agents have a water-soluble property, they are inclined to elute into processing solutions during processing, often causing stain or sludge. Because of this, when these high molecular weight elctrolytes or surface active agents are used, one having large water-solubility was selected or means to bridge the high molecular weight electrolytes was adopted. However, when the amount of replenishment is made reduced they cannot solve the problems of staining and sludging. In order to eliminate these disadvantages, Japanese Patent Publication No. 60-49894(1985) proposes a technology of using water insoluble crystalline metal oxide particles together with hydrophobic binders such as vinylidene, etc. In this case, the hydrophobic binders have no electro-conductivity, in order to confer conductivity it is necessary for the filling ratio of the particles in the conductive layer to be increased, and in this reference 80% by weight or more has been proposed. However, crystalline metal oxide particles scatter light and, therefore, application thereof to silver halide light-sensitive materials causes a problem of devitrification. Particularly, application to light-sensitive materials, which comprise a transparent support coated thereon with a light-sensitive emulsion layer, is difficult. In order to overcome this problem of devitrification, Japanese Patent Publication No. 3-24656(1991) proposes using a hydrophilic binder and a nonionic surface active agent together with the crystalline metal oxide particles, and Japanese Patent Publication No. 3-24657(1991) proposes the use of a hydrophilic binder and fluorinated-type surface active agent together with the crystalline metal oxide particles. However, with these technologies, in order to confer electro-conductivity, it is shown that filling ratio of at least 50% is necessary. Problem of devitrification may not be solved satisfactorily, and, moreover, since these technologies necessitate the use of a water-soluble anti-static agent, they also have problems of staining of processing solutions and generation of sludge.
It has been investigated on light-sensitive materials which do not cause sludge in the processing solution, while maintaining good anti-static performance, have unexpectedly found that adhesion of sludge to the light-sensitive material is remarkably reduced when impedance of the light-sensitive material, which is one of electric properties of the light-sensitive material, is made at a certain value or thereabove, and the amount of replenishment of the processing solution is at a certain level or therebelow.
Thus although various attempts to overcome the detriment of plastic films caused by static electricity have been made for a long time, and relation between mechanism of generation and material has remained unknown, and, particularly in the field of photography, in which such a detriment often turns out to be fatal, it has long been selected to be the best means, for example, to provide by coating electroconductive metal oxides as an electroconductive layer.
However, as regards light-sensitive photographic materials provided with a electroconductive layer containing electroconductive metal oxide particles, lots of problems have still remained unsolved, notwithstanding various researches have been made as a means for improving degradation of photographic performance under low humidity condition for a period over 30 years, up to today, since disclosure in Japanese Patent Publication No. 35-6616(1960).
For example, when a layer containing such an electroconductive metal oxide particles is provided adjacent to a silver halide emulsion layer, fogging by pressure or scratch marks are likely to take place in the image due to friction during manufacturing or processing operations. When, as another example, it is used by together with a polymer binder, since the fine particles which are present on the surface easily fall away behind, leaving a problem of spoiling products during manufacturing procedure by adhesion to transport rulers. Still further, as those materials comprising metal elements as the main ingredient generally have relatively high specific gravity, often causing a problem of precipitation during coating on the light-sensitive photographic materials, which also cause problems of uniformity of coating solutions, preservation, etc.
Most of these problems may be solved by making the particles finer, however, preparation of finer particles causes the following new problem. That is to say, they are problems of increased viscosity of coating solutions, problems of operation caused therefrom, problem of precipitation of particles caused by increase in cohesion power, etc. It is possible to solve the problems of viscosity increase of coating solutions and precipitation of coagulated particles by reducing adding amount of addition of the electroconductive particles and reducing concentration, respectively. However, simple reduction of the amount of the electroconductive particles is likely to lead degradation in anti-electrostatic performance.